AT ITS HEART, “THE VOICE” IS A GAME SHOW, and the most essential rules that guide its coaches are unspoken: Try not to wince when blind auditions trick you into picking an unsightly singer; always declare it “heartbreaking” to choose the winner of a vocal battle, no matter how easy the decision actually is; and most importantly, never, ever interrupt Christina Aguilera when she is speaking.

One late afternoon in a quiet backroom of a Los Angeles photo studio, Aguilera is curled up, barefoot, on a white couch next to fellow coaches Adam Levine and Blake Shelton. She’s sipping an iced coffee and holding forth on the greatness of the team of singers she’s assembled for The Voice‘s second season, which begins February 5th in a prime post-Super Bowl slot: “In one of my battles,” she says, “this girl and guy are doing Nirvana’s ‘Heart-Shaped Box,’ and I’m not sure if people would even expect that from me…”

At that, Cee Lo Green – who’s been splayed diagonally in a leather chair off to the side, in deep communion with the ceiling – snaps to attention and begins singing Kurt Cobain’s melody in his high voice: “Hey, wait/I’ve got a new complaint…”

Aguilera flares up like a sexy puffer fish, swiveling her bleach-blond head in his direction, red lips pursed, blue eyes blazing with imperial annoyance. “Yes, Cee Lo,” she says, as if she’s talking to her four-year-old son. “This is my floor here!”

He stops singing, and Aguilera laughs, already over it: “You wake him up and now he’s interrupting everybody’s shit!”

The unlikely stars of The Voice – last season’s highest-rated NBC entertainment show – have a surprisingly warm off-camera rapport for four people who have no real business being in a room together. “Just look at the four of us,” says Levine. “It’s just so wrong and so amazing.”

As widespread gossip would have it, the other three supposedly resent Aguilera for various alleged sins, including tardiness, imperiousness and earning more money than them – but there’s not much evidence of that today. “‘Supposedly’ is the key word,” Aguilera says, with a big laugh. Levine and Shelton just attended Aguilera’s 31st birthday party at a Hollywood bowling alley; Cee Lo skipped it only because he was out of town.

They spend a lot of time teasing one another. Oklahoma native Shelton – a singer with 10 Number One country hits to his name but little recognition outside his genre before The Voice debuted last April – is a frequent target of hick jokes. Shelton, 35, has been on an Eighties kick lately, so he plays Young MC’s “Bust a Move” on his iPhone’s tinny speakers. Says Levine, “Blake thinks this song came out two weeks ago.” But they’re also jealous of his cowboy cool: “Blake can say anything or do anything,” Levine adds. “If I was like, ‘I’m drunk at 4:00!’ I’d be attacked. He’s like, ‘It’s cool, fuck you, I just shot a fucking moose, kiss my ass!’ He can say whatever he wants.”

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Cee Lo, 37, is the designated oddball, the ruler and sole inhabitant of what Shelton calls “Cee Lo Land.” At the moment, he’s wearing a black tank top and long black shorts, plus sandals over white socks. “He can wear white socks with sandals and still have it be fucking cool,” says Levine. “If I did that, Blake would make fun of me.”

If Aguilera occasionally has to go full diva, on-camera or off-, she sees it as the only way to hold her own. “You have to be a pretty strong girl to stay up in the mix with the guys,” she says. “It’s a lot. It’s a crazy locker-room kind of situation.”

Levine, his tattooed, yoga-toned arms exposed by a sleeveless shirt, turns to Aguilera. “I honestly just recently started realizing that you’re surrounded by three dudes all the time, and that has to be something of a pain in the ass,” he says. But they’ve made some concessions: “We stopped farting in front of her!”

Aguilera rolls her eyes: “You had a nasty burp at the Super Bowl commercial, though.”

BESIDES ONIONS, TOMATOES and marijuana, the Netherlands’ biggest cash crop may well be reality shows. Big Brother and Fear Factor both start­ed there before spreading around the world, and in 2010, the creator of those shows, the very wealthy John de Mol, in­troduced another one: The Voice of Hol­land. He was convinced that the Amer­ican Idol/X Factor formula was played out. Says de Mol, “The trick that worked for many years — a professional jury kill­ing a totally untalented 16-year-old boy with braces who thinks he is Michael Jackson — started to show weak spots because people foresaw the tricks and the structure.”

Instead, he had a team of produc­ers spend more than a year developing new tricks, chief among them a now-fa­mous audition process: Coaches sit in red chairs with their backs to audition­ing singers, turning around at the press of a button when they’re impressed. They also eliminated the William Hung ele­ment entirely, instead drawing from a sol­idly talented pool of contestants, includ­ing referrals from Universal Music Group talent scouts. The other twist never fails to make compelling TV: When more than one coach wants a contestant for their team, the power dynamic shifts, with rich and famous coaches forced to supplicate themselves before an unknown.

The American Voice is almost iden­tical to the Dutch version, albeit with coaches more internationally famous than the likes of Angela Groothuizen and Roel van Velzen. But it could have been a dif­ferent show altogether: Reality auteur Mark Burnett had been working on his own idea for a competition, where celebri­ty coaches would also have fielded teams of singers, when Paul Telegdy, president of NBC’s alternative and late-night pro­gramming, brought The Voice of Holland to his attention.

They decided to drop their own idea and instead try to import The Voice — and while CBS also had interest in the show, de Mol was more inclined to go with NBC, which has been mired in fourth place among broadcast networks. “NBC was not the first network you would think of,” says de Mol. “But I felt NBC was the right place because they needed a hit so badly, so they would give it support.” NBC got it — and gave Burnett just four months to find judges, assemble a production team and put it on the air.

ADAM LEVINE DOESN’T have a cold, or so he keeps insisting. “I’m not actually sick, I swear to you,” he says, blowing his nose in the West Holly­wood studio where he’s spending a 12-hour day filming an endless series of men­toring sessions with members of his team. “My allergies are driving me crazy,” says Levine. “Celebrities are just like us — they have boogers.”

For the first part of the day, Levine — in a white V-neck and jeans — and guest coach Robin Thicke stand by a gleaming black piano (a crew member runs in to pol­ish it between every take) in a huge studio, helping the contestants through stripped-down versions of battle-round songs. They have to pretend that the numerous cam­eras that swarm them aren’t there, which can be tough: As one contestant — a tall blond girl from Kansas with a wispy voice — struggles to engage in “natural” banter with Levine and Thicke, a crew member barks, “Take a step to your left!” She jumps.

At lunchtime, Levine heads into a trailer devoid of personal effects and begins eat­ing a mix of grains, kale and salmon from a plastic container. “I like to eat healthy because I like to feel good,” he says. “A big part of sustaining your own life is not to feel like shit.”

Levine, 32, isn’t feeling great at the mo­ment, what with the allergies and the fact that he was out late drinking the night before (he left a voicemail message of him singing Erykah Badu’s “Tyrone” on a friends phone). But he has a job to do — which still unsettles him. “I never thought that I would be someone that worked,” he says, kicking his feet up on a faux-wood counter. “I always thought that I had es­caped having to work by being in a band. I should be living the rock & roll lifestyle that everyone thinks I live!”

When Burnett approached Levine about the show, he was feeling restless. “When I turned 30, I started thinking to myself, like, ‘Oh… what the hell have I been doing my whole life?’ And I was like, ‘No, man, there’s a million things I wanna do with my life. I’m gonna do ’em.’ And The Voice was a huge part of realizing that in myself.”

At the same time, Maroon 5 seemed to have plateaued. “We felt slightly stag­nant,” he says. “We felt like, we’ve had hits, we’ve had songs that have gone no­where, a lot of ups and downs. We’re on the road, maybe we’re not playing to the biggest crowds we’ve played to in our lives. It’s not gone down the shitter, but it’s definitely not as big as it once was.” Levine says his bandmates supported the new gig, seeing the show as a chance to get renewed attention — even though it meant rescheduling some tour dates. It was a smart bet: During the season, Ma­roon 5 debuted “Moves Like Jagger,” the Aguilera-featuring tune that has become one of their biggest songs ever.

Always a competitive dude — he used to spend hours battling his bandmates at Halo — Levine came in determined to win. “I thought to myself, ‘If I’m going to do this, I’m going to do this 100 percent.’ I won’t fuck around. I want to be as present doing The Voice as I am onstage. So I decided that really early on. I had conversations with everyone else, and they were like, ‘Holy shit, man, you really care about this.'”

Levine quickly showed himself to be as smooth a TV presence as he is a frontman — able to schmooze the best singers to join his team. “I finally got a chance to talk,” he says. “Singers don’t get to talk. I’m rel­atively articulate and I felt like maybe I deserved a shot at letting people know that.” Frustrated by his slickness, Aguilera called Levine a used-car salesman on camera — which began their habit of on­screen bickering. The apparent conflict — which sometimes seemed more like flirt­ing — fueled rumors of a feud and lent a certain charge to her appearance on “Moves Like Jagger.”

“I don’t have problems with Christina,” Levine says. “Anyway, if I did, I wouldn’t tell you! The problems that I face on a daily basis are all little stupid things that aren’t gonna affect our relationship in the long run. Being pissed off that Christina’s late, which, like… yeah, she’s been late a bunch of times. She got better at it. So, I’m not mad about it anymore, you know? We’re playful. I know as much as people don’t want this to be true, there are no problems between us. I hope that’s the case on her side too. I feel like it is. We have conversations after the show and we’re just like, hanging, and it’s all good. So it’s fine.”

Soon, Levine’s lunch hour is over, and he has to change into a different V-neck for further mentoring segments — these are called “sit and chats,” and they drag on and on. Between takes, he shows Thicke a picture of his Victoria’s Secret-model girl­friend (“We’ve been together two years. For me, that’s like, forever”), repeats Chris Rock routines and complains about over­ly busy drummers: “They all wish they were in Dave Matthews Band.” After sev­eral contestants complain about nerves, he muses, “It was so different last year. No one knew what this was, so no one was scared. Now it’s The Voice and everyone’s flipping out.”

As the crew takes Levine over for yet an­other set of segments, he gives an exagger­ated moan. “I want to die,” he says, start­ing to get punchy.

“Can I at least get a handy while we do this? Who’s got the lube?” he adds, perhaps backing up Aguilera’s locker-room argu­ment. “I need a scotch and a BJ!”

CEE LO GREEN SCANS HIS hotel’s room-service menu, and shakes his head. “It’s all a little froufrou for me,” he says. He’s in a 54th-floor Manhattan hotel suite, where remote-controlled curtains have parted to reveal a Hudson River view. He’s wearing an enormous white T-shirt and dark track pants; he’s covered in a maze of tattoos, including the word THINK on his right wrist and the word TWICE on his left (it’s a reference to a line from Gnarls Barkley’s “Crazy” and also, as he notes, “gener­al good advice”).

Eventually, he decides on a Cobb salad, but thinks twice: “Is avocado good for you?” Cee Lo is trying to watch what he eats — and not because of Levine’s habit of poking his impressive belly and saying, “We’ve got to close down the grocery store.”

“I’m just a naturally big guy,” Cee Lo says. “I don’t know if I want to get as small as Adam. I don’t think that’d work for me. I don’t want to disappoint the ladies. They truly do love me just as I am.” (Though lately, he adds, he’s hardly had time for that. “We work so hard that I’ll be lucky to get a massage with a happy ending!”)

“But I want to be healthy. I lost a few really good friends, though it wasn’t all about their weight. I lost my friend Heavy D recently, and I was friends with Patrice O’Neal. So it’s just like, I’m looking at them and noticing the similarities. I want to be as healthy as possible. I’ve got a young son and I want to be around for him.”

Cee Lo is also in near-constant pain from a slipped disk in his back, a condi­tion that’s only aggravated by his relent­less traveling. The Voice is a chance to earn a living without touring — and he’s looking into a Las Vegas residency as well.

On a less practical level, he sees his pres­ence on the show, belly and all, as a tri­umph “for regular people. I feel like there are so many images and false idols. I feel like someone like myself is toppling those things over. We are the majority. This is our power, this is our time. I feel wonder­ful and strange and bizarre and unique and all those kinds of things. And I do feel beautiful. It goes back to Sly Stone: Every­body is a star.”

SOME STARS CAN’T HELP shining brighter than oth­ers, however — as Aguilera demonstrates while shoot­ing her own mentoring ses­sions. “I just want to be here to support and encourage you guys,” Agui­lera tells one pair of singers, a preppy dude with a powerful operatic voice and a curly-haired woman who seems influenced by Celine Dion. They’re in a rented Silver Lake mansion, standing beside a piano un­derneath a crystal chandelier. Aguilera casually demonstrates a high note for them — and the sound that comes out of her throat is so pure, piercing and huge that it practi­cally knocks her team members out of the room. “I get loud,” she says later, giggling.

As Burnett rushed to put The Voice to­gether, he heard one thing over and over from his colleagues: “You’ll never get Chris­tina Aguilera for this show.” But he saw her as essential to establishing the show’s brand and credibility — “I said to myself, ‘Christina Aguilera is the voice of her gen­eration'” — and he pushed for a meeting. She signed on after Burnett assured her there would be no Simon Cowell-style hu­miliations on the show.

Aguilera had just come off what she calls “a rough year”: In 2010, she got divorced, released an album (the synth-y Bionic) and movie (Burlesque, with Cher) that were both poorly received, and canceled a tour. “Going through a divorce, anybody would have a difficult time,” she says, “but being a female under the microscope in the public eye, it was that much harder.”

She started feeling she “needed to take a break from myself for a second. At that point, I really didn’t know the show was even going to be as big as it was. It was more like, ‘This is a really cool concept in a way that I can experience something out­side of myself and give back and maybe be able to inspire myself as an artist again.'”

After a long career of her own, Aguilera particularly loved The Voice‘s inclusion of older contestants who may have already gone through a record contract or two. “It’s nice to give people second chances,” she says. “It’s a great opportunity to give peo­ple new life and jump-start not only them but your heart and your spirit for this busi­ness again.”

Not coincidentally, she’s been working on a new album of her own. “I only make records when I’m really passionate and have something to say, and I have a lot to say, with the time that was taken off since my last record — a couple of years. I have a lot of shit, a lot of crazy shit.”

For a woman who once strutted in back­less leather chaps (in the “Dirrty” video, which Cee Lo shamefacedly counts as a fa­vorite), Aguilera can be unexpectedly vul­nerable. She likes that The Voice shows “a softer side” of her — and it’s done the same off-camera. She was chatting with Shelton at an after-show party at his house last season when she suddenly said to him, “I don’t think you like me.” Shelton called over his wife, singer Miranda Lambert, who revealed that Shelton’s birthday gift a couple of years back was an autographed Aguilera tour book. “She’s my favorite fe­male vocalist,” says Shelton (who also ad­mits to having had a “major crush” on her — he had even designated her as a marital “free pass,” never expecting to meet her). “I told Christina that, and I’ll never forget the look on her face. Of course, knowing Christina now, probably somebody that works for her signed that autograph.”

While the guys hang out on set, Agui­lera often heads to her trailer to spend time with her son, Max. “Christina, I don’t know why they give her so much shit,” says Cee Lo. “But she’s cool. She’s quiet. She wants to be a success at everything, including being a mother. I have not had any negative energy from her. It’s mainly because she’s not really around. She just spends a lot of time in her corner. We’re guys, so we’re out drinking beers and talk­ing shit — seemingly we get along a lot bet­ter. But she hardly ever hangs out with us. She’s kind of focused on going about her business. And I can respect that. And I know that she is a business, just by watch­ing her. She has about 17 people around her at all times!”

As far as Aguilera is concerned, you can go ahead and call her a diva. “Of course. Hello! Do you know who you’re talking to? I’m a female, I’m very assertive and also I’m working on a show called The Voice and I’m known for being sort of a powerhouse vocalist — and I’m sorry, but a great vocalist in my time — so you do get pigeonholed and titled ‘diva.’ And if that just means being an assertive woman and knowing what you want, I will gladly wear that title to the day I die.”

But she does her best to ignore gossip about the show, and her life. “At this point, you could throw anything at me, and it’s not going to stick,” she says. “Everything outside of my home and my vision and my goals for myself is noise. I keep my focus on where I want to go in my career. The train ain’t slowing down anytime soon. I want to be on that stage, 80 years old, singing some old blues song, with a cane, and croak that way, when it’s my time.”

LEVINE TAKES A DEEP breath, glances at his fel­low coaches, and goes for it. “This is going to sound disgusting and barf, but I have to say, I have nothing but love for you guys. I’m serious!”

Aguilera touches his arm. “Aww, Adam!” She likes to remind him that he didn’t ac­tually win anything last season — it was Ja­vier Colon who triumphed. “I agree with you,” Levine says. “I didn’t win shit. I don’t get my Voice prize in the mail…. I peaked too early and now I’m fucked!”

Cee Lo suddenly straightens up again in his chair and asks the other three, “How long do you guys think that you could go on with the show?” They gape at him.

“Why are you asking that?” Aguilera says. “This is not a good question right now, it’s going to be on tape!”

“I was asking myself that the other day,” Cee Lo continues, innocently, “because this is so great, it could last.” (For the record, de Mol suggests that changing a judge or two after a couple of years could “bring in a new sparkle,” and NBC entertainment chairman Bob Greenblatt says, “We love these coaches, but if for whatever reason one of them said, ‘I really don’t know that I can do it this year,’ we would try to find somebody to replace them. And I think the show could certainly go on if that had to happen.”)

Aguilera sighs. “I don’t think this is the time or place to discuss that, Cee Lo!”

“I could do this show forever,” Cee Lo says.

Levine can’t take it anymore, and he reaches for my digital recorder. “Shut this fucking thing off,” he says.

Instead, I ask Aguilera if she could suc­cessfully coach her fellow coaches. “Maybe not coach them, but do other things,” she says. “Like, spank them all.”

“Whoa!” says Cee Lo, clearly pondering visions of “Dirrty.”

“Not like that,” Aguilera says, and all the guys groan in disappointment. “But they all deserve spankings.”